MOSCOW — As global warming makes exploration of the Arctic sea floor possible for the first time, Russia has launched a massive expedition to help secure the region’s vast resources.

In the next few days, two manned minisubs will be sent through a hole blasted in the polar ice to scour the ocean floor nearly three miles below. They will gather rock samples and plant a titanium capsule containing the Russian flag to symbolize Moscow’s claim over 460,000 square miles of hitherto international territory — an area bigger than France and Germany combined in a region estimated to contain a quarter of the world’s undiscovered oil and gas reserves.

The issue of who owns the North Pole, now administered by the International Seabed Authority, has long been regarded as academic since the entire region is locked in year-round impenetrable ice. But probably not for much longer.

The area of the Arctic Ocean covered by ice has been shrinking since the early 20th century and the change has accelerated in the past decade, according to the U.S. National Oceanic and Atmospheric Administration. Some scientists blame the shrinkage on the effects of human-driven climate change.

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As the Arctic’s ice recedes, its waters are becoming more navigable — and its riches more accessible to a resource-hungry world.

“The No. 1 reason for the urgency about this is global warming, which makes it likely that a very large part of the Arctic will become open to economic exploitation in coming decades,” says Alexei Maleshenko, an expert with the Carnegie Center in Moscow. “The race for the North Pole is becoming very exciting.”

The U.S. Geological Survey estimates that 25 percent of the world’s undiscovered oil and gas reserves lie beneath the Arctic Ocean. Experts at the Russian Institute of Oceanology calculate that the saddle-shaped territory that Russia is planning to claim may contain up to 10 billion tons of petroleum, plus other mineral resources and vast, untapped fishing stocks.

The 1982 Law of the Sea Convention establishes a 12-mile offshore territorial limit for each country, plus a 200-mile “economic zone” in which it has exclusive rights.

But the law leaves open the possibility that the economic zone can be extended if it can be proved that the seafloor is actually an extension of a country’s geological territory.

In 2001, Russia submitted documents to the United Nations claiming that the Lomonosov Ridge, which underlies the Arctic Ocean, is an extension of the Siberian continental shelf and should therefore be treated as Russian territory. The case was rejected.

But a group of Russian scientists returned from a six-week Arctic mission in June insisting that they had uncovered solid evidence to support the Russian claim. That paved the way for the current expedition, which includes the giant nuclear-powered icebreaker Rossiya, the huge research ship Akademik Fyodorov, two Mir deep-sea submersibles — previously used to explore the wreck of the Titanic — and about 130 scientists.

The subs were tested Sunday, near Franz-Joseph Land in the frozen Barents Sea, and found to be working well.

“It was the first-ever dive of manned vehicles under the Arctic ice,” Anatoly Sagelevich, one of the pilots, told the official ITAR-Tass agency. “We now know that we can perform this task.”

The upcoming dive beneath the North Pole will be far more difficult, and involve collecting evidence about the age, sediment thickness and types of rock, as well as other data — all of which will be presented to the United Nations Commission on the Limits of the Continental Shelf (a body of scientists chosen by parties to the Law of the Sea Convention) to support Russia’s claim to the territory.

The longer-term goal, Sagelevich says, is to get used to permanently working in that environment.

Russia’s push to the pole is being led by Artur Chilingarov, 68, perhaps the nation’s most famous living Arctic and Antarctic explorer and deputy speaker of the lower house of parliament. He was named a Hero of the Soviet Union for leading a 1985 expedition in the Southern Ocean, in which his vessel became locked in sea ice.

Despite the melting trend, this summer’s ice pack is thicker than anticipated and may hamper the mission.

Emboldened by surging oil revenues, the Kremlin has in recent years revived the Soviet-era practice of direct economic, scientific and geopolitical competition with the West. In the case of the Arctic seabed, at least, some nations seem ready to respond in kind.

Denmark’s scientists hope to prove that the Lomonosov Ridge is an extension of the Danish territory of Greenland, not Russia. Thorkild Meedom of Denmark’s Ministry of Science, Technology and Innovation said Canadian and Danish scientists on two icebreakers are now conducting mapping studies of the north polar sea.

“We’re going step by step and mapping as conditions permit,” Meedom said. “You have to keep in mind that it is an extremely difficult region and very hard to collect data.”

Nations that border the Arctic are concerned about security as well as energy. The U.S. Navy and Coast Guard co-sponsored a symposium in Washington this month titled “The Impact of an Ice-Diminishing Arctic on Naval and Maritime Operations.”

And Canadian Prime Minister Stephen Harper said earlier this month that Canada plans to spend $7 billion to build and operate up to eight Arctic patrol ships.

“In defending our nation’s sovereignty, nothing is as fundamental as protecting Canada’s territorial integrity” at a time of rising oil, gas and mineral prices, he said.

Canada, which has the second-longest Arctic coastline, is also conducting a $70 million project to map the seabed on its side of the Lomonosov Ridge, in what might be a prelude to its own submission to the U.N.

The U.S. could claim Arctic territory adjacent to Alaska, but is hampered by Congress’ failure so far to ratify the Law of the Sea Convention.

Three years ago, U.S. lawmakers were already warning of the detrimental impact of failing to ratify the Convention. In a May 2004 speech advocating ratification, Sen. Richard Lugar, R- Indiana, then chair of the Senate Foreign Relations Committee, told his audience at Washington’s Brookings Institute that the U.N. “will soon begin making decisions on claims to continental shelf areas that could impact the United States’ own claims to the area and resources of our broad continental margin.”

He specifically mentioned Russia’s ambitions, as well.

“Russia is already making excessive claims in the Arctic,” said Sen. Lugar. “Unless we are party to the Convention, we will not be able to protect our national interest in these discussions.”

Some experts fear the potential for conflict over Arctic territory and resources, and the Russian media highlighted reports of a “U.S. spy plane” that allegedly shadowed the North Pole expedition this week. But others say existing international law is adequate to enable boundaries of influence to be negotiated between the key players as global warming unlocks the north’s treasures.

“I don’t see why this issue should worsen relations between Russia and other countries,” says Pavel Zolotaryov, deputy director of the official Institute of USA-Canada Studies in Moscow. “We can solve our differences on the basis of information. And after this expedition], Russia will be able to say that we’ve been there and conducted the research” to bolster Russia’s claims in the region.